1. Technical Field
The present invention relates to a sunscreen that is topically applied using a cleanser. More particularly, the present invention relates to personal cleansing compositions having photoprotective agents which consist of chemical sunscreens, physical sunscreens, or both in combination, one or more cleansing agents, and a vehicle for enhancing absorption into the wearer's skin.
2. Discussion
Modern science has become acutely aware of the effects of the sun on human skin, particularly in the latter part of the twentieth century. Of particular concern is that form of solar radiation which occupies the range between 290 and 400 nm, ultraviolet radiation. Overexposure of the human skin to ultraviolet radiation has many deleterious results. One such result of acute overexposure is sunburn, which is felt to be a risk factor in the development of melanoma skin cancer. Serious results of chronic overexposure include premature aging (photoaging) of the skin, the development of precancerous growths (actinic keratoses) and the development of nonmelanoma skin cancers such as basal cell or squamous cell skin cancers.
Two sub-bands of ultraviolet radiation which penetrate the atmosphere are generally known. The first is ultraviolet A (UVA) in the 320 to 400 nm band, and the second is ultraviolet B (UVB) in the 290-320 nm band. (There is also ultraviolet C, but this radiation is absorbed by the earth's atmosphere and does not reach the earth's surface.) Ultraviolet A represents a wider nm scope and is more penetrative in the skin (160-250 .mu.m) than is ultraviolet B (17-49 .mu.m). However, it is ultraviolet B which is believed to pose the greatest threat to the human skin in terms of sunburn, aging, and skin cancers. Regardless, ultraviolet radiation of all types can cause the generation of damaging free radicals. These molecular fragments are highly reactive and are known to degrade human tissue by causing destruction at both cellular and molecular levels.
Modern lifestyle has contributed to skin damage due to increased exposure to ultraviolet radiation. It is believed that there are at least two reasons for the heightening of the problem. First, while the early part of the present century taught that fairness of skin, as an attribute of the privileged class, was a desirable feature causing people to avoid exposure to the sun, attitudes changed by the 1920's such that a "healthy tan" began to be regarded as a desirable feature. Suntanning became a popular pastime, and bathers began to seek out sunny climes. Outdoor activities such as golf, camping, tennis, and swimming also captured increased interest in the 1950's.
As a practical matter, ultraviolet exposure occurs during all daylight hours, and includes both reflected and direct light. In reality, the majority of sun exposure during one's lifetime most probably occurs when people are not paying attention--at school or work, on a playground, out shopping, while talking to a neighbor out-of-doors, even while driving a car. The fact is that we are exposed to ultraviolet light from almost every direction every daylight hour. (The inventors regard this as "insensible" exposure.)
A second possible reason for the increase of damage due to ultraviolet radiation is due to the increase of ozone layer-destroying atmospheric pollutants primarily in the forms of chlorofluorocarbons and halogens. The negative impact on the ozone layer by these chemicals has led to increased amounts of ultraviolet radiation actually reaching the earth's surface and, coincidentally, the human population.
Efforts to counteract the damage effected by ultraviolet radiation have primarily included (1) avoidance of sunlight, particularly during certain times of day (particularly peak sunlight hours), (2) the wearing of appropriate clothing to physically block the sun, and (3) topically-applied sunscreen lotions, gels, creams, and sprays. Sometimes the first approach is impossible, particularly during the summer months when many activities are held out-of-doors. The second approach is probably underutilized, but in any event is not always practical.
The third approach--topically applied compounds--have demonstrated varying degrees of effectiveness. These compounds are readily available yet are underutilized for a variety of reasons, including inconvenience and feel. The consumer may select from a host of different products available in the marketplace. Selections are typically made based upon the sun protective factor (SPF) rating of the product, the SPF value providing a guide as to the effective UVB protection the particular selection would offer. Selections can also offer "broad spectrum" coverage which would include protection from UVA radiation as well. A standardized method for quantifying UVA protection is not currently in use.
Topical sunscreen products have SPF values in a wide range, with values typically between 2 and 60. "SPF" is defined as the ratio of the time of UVB exposure necessary to produce minimally detectable erythema in sunscreen-protected skin to that time for unprotected skin. The SPF is inversely proportional to the amount of UVB which passes through to the cutaneous surface. A product having an SPF value of 2 reduces ultraviolet B radiation exposure to the skin by 50% by allowing 1/2 of UVB to penetrate, while a product having an SPF value of 4 presents a reduction of 75% by allowing 1/4 or 25% of UVB to penetrate. An SPF value of 15 demonstrates a reduction of ultraviolet B exposure by over 90%, while exposure is reduced in excess of 98% when the SPF value is 60.
These numbers, however, may be misleading. It is believed by many that only those products having SPF values of 15 or over are of value to the wearer. While it is true that higher SPF factors offer significant protection when used, such products are usually applied only in anticipation of intense sun exposure. It is, in fact, the total sunlight exposure over the person's lifetime which determines the risk of photodamage and most skin cancers. It may not be intense sun exposure during recreational activity which contributes greatest to this lifetime exposure, but daily, constant, intermittent, insensible exposure to the sun that contributes most significantly to the lifetime accumulation of photodamage. Accordingly, the consistent use on a daily basis of lower SPF sunscreens could result in a decrease in the lifetime UVB radiation exposure compared to the inconsistent use of higher SPF photoprotectants. This is especially true once again in that sunscreens are most often used only on days of anticipated high-level exposure and usually not at all on most days.
In addition, consistent daily sunscreen use may delay the onset of skin cancers. It is felt that many years often intervene between sun exposure and skin cancer onset. It is thus proposed that the constant use of sunscreen of SPF 16 could theoretically delay the onset of squamous cell carcinoma until the age of 600 years. Along these lines, one need only regularly apply (through daily application) a product having an SPF value of 4 throughout one's life to prevent the onset of squamous cell skin cancer due to ultraviolet radiation until well beyond the normal life span. (Marks, The Use of Sunscreens in the Prevention of Skin Cancer, presented to the Menzies Foundation Conference, Hobert, Australia, Sep. 9-11, 1996.)
It is important to note that sunscreens of any type are not recommended as the primary source of protection from ultraviolet radiation, but as an adjunct to proper skin protection offered by clothing and through measures directed to the avoidance of unnecessary exposure.
The action of a topical sunscreen product is generally based upon one of two mechanisms: Chemical absorption or physical blocking. Chemical sunscreens typically include one or more ultraviolet-absorbing chemical components, such as a benzophenone, a salicylate, or a cinnamate provided in various levels of concentration. While generally effective at absorbing ultraviolet B radiation, these products may fail to effectively protect against ultraviolet A radiation. These products have also been reported to occasionally cause a reaction to the wearer.
As an alternative to the chemical sunscreen, so-called physical or inorganic sunscreens are known. These products utilize particles of zinc oxide or titanium dioxide suspended in a carrier for topical application and physically scatter, reflect, and absorb ultraviolet radiation. The inorganic sunscreens provide effective protection against both ultraviolet B and ultraviolet A radiation. However, because of their white appearance (titanium dioxide is used a white pigment in paints, rubber and plastics), these sunscreens have the significant drawback of leaving the wearer appearing to have been painted white. By micronizing the zinc oxide and titanium dioxide particles, it is possible to eliminate the ordinary white coating and provide a substantially clear coat.
Regardless of form, the known topical sunscreens share a common undesirable characteristic--inconvenience. Topical sunscreens, whether chemical- or physical-based, are time-consuming to apply, and tend to be oily and uncomfortable to wear. Despite increasing public awareness of the value of daily photoprotection, the fact is that over 70% of Americans do not apply sunscreens, hence most people still face the ravages of daily exposure to ultraviolet radiation without protection. (U.S.A. Weekend, Mar. 6-8, 1998, under caption "A Nation That Takes Health Risks.")
Aware of this drawback, efforts have been made in the past to vary the method of applying a sunscreen to the wearer. Examples of the variety of these approaches are presented in: U.S. Pat. No. 5,547,659, issued on Aug. 20, 1996, for PHOTOPROTECTION COMPOSITIONS; U.S. Pat. No. 5,545,399, issued on Aug. 13, 1996, for COSMETIC COMPOSITION; U.S. Pat. No. 5,518,712, issued on May 21, 1996, for WATER RESISTANT SUNSCREEN PROTECTION AND INSECT REPELLANT; U.S. Pat. No. 5,505,935, issued on Apr. 9, 1996, for SUNSCREEN COMPOSITIONS; U.S. Pat. No. 5,487,884, issued on Jan. 30, 1996, for PHOTOPROTECTION COMPOSITIONS COMPRISING CHELATING AGENTS; U.S. Pat. No. 5,486,352, issued on Jan. 23, 1996, for SUNSCREEN COMPOSITIONS; U.S. Pat. No. 5,456,904, issued on Oct. 10, 1995, for PHOTOPROTECTION COMPOSITIONS COMPRISING CERTAIN CHELATING AGENTS; U.S. Pat. No. 5,384,115, issued on Jan. 24, 1995, for PHOTOPROTECTION COMPOSITIONS COMPRISING A RADICAL SCAVENGING COMPOUND AND AN ANTI-INFLAMMATORY AGENT; U.S. Pat. No. 5,306,485, issued on Apr. 26, 1994, for SUNCARE COMPOSITIONS; U.S. Pat. No. 5,244,665, issued on Sep. 14, 1993, for COSMETIC COMPOSITION; U.S. Pat. No. 5,219,558, issued on Jun. 15, 1993, for PHOTOPROTECTION COMPOSITIONS HAVING IMPROVED SUBSTANTIVITY; U.S. Pat. No. 5,215,749, issued on Jun. 1, 1993, for COSMETIC COMPOSITION; U.S. Pat. No. 5,208,011, issued May 4, 1993, for ULTRAVIOLET RESISTANT SUNSCREEN COMPOSITION; U.S. Pat. No. 5,207,998, issued on May 4, 1993, for SUNCARE COMPOSITIONS; U.S. Pat. No. 5,196,187, issued on Mar. 23, 1993, for COSMETIC COMPOSITION; U.S. Pat. No. 5,188,831, issued on Feb. 23, 1993, for SUNSCREENS CONTAINING BOTH WATER AND OIL DISPERSIBLE TITANIUM DIOXIDE PARTICLES; and U.S. Pat. No. 5,028,417, issued Jul. 2, 1991, for SUNSCREEN COMPOSITIONS, all incorporated by reference herein.
While representing improvements in the art of sunscreen application, these references fail to provide an effective sunscreen-soap combination which demonstrates appreciable efficacy, longevity, or substantivity.